The present, invention relates to a flaky particulate material and a cosmetic composition.
Flaky particles are excellent in adhesion to skin, and also excellent in smoothness owing to their shapes. Thus, such flaky particles can provide great comfort of use, and therefore, are widely used in makeup cosmetics.
A variety of flaky particulate materials are known as such flaky particles. Among them, particulate materials with a small coefficient of friction provides excellent smoothness, and thus, a cosmetic composition that provides great comfort of use can be obtained from such flaky particulate materials. A flaky particulate material with a particularly small coefficient of friction is, for example, boron nitride, which is mentioned in Patent Document 1.
Boron nitride has indeed good smoothness, but it is somewhat whitish. Thus, the boron nitride has a defect that it looks whitish, on skin upon use. For giving skin a natural tone, it is difficult to increase a formulation amount of boron nitride in cosmetic compositions. On the other hand, other flaky particulate materials such as talc, mica, sericite, barium sulfate, or aluminum oxide, are inferior to boron nitride in smoothness, although they are superior in transparency. That is, no flaky particulate material suitable for a cosmetic composition providing high transparency, and sufficient smoothness comparable to boron nitride, has been known yet in the art.
Patent Document 2 discloses a surface-treatment of boron nitride particles with a fatty acid metal salt for improving comfort of use, adhesion, and persistence of make up, of the particles. However, such a surface-treatment is unsuccessful to improve transparency of boron nitride particles, and thus, cannot produce a flaky particulate material with both sufficient transparency and smoothness. An alternative treatment, which includes a surface-treatment of a pigment for a cosmetic composition with a fatty acid metal salt, have been also known (See Patent Document 3, for example), but the treatment is intended for enhancing dispersibility of the pigment, or providing adhesion or water repellency to the pigment. Thus, no report specialized in an improvement of smoothness has been found yet in the art.
[Patent Document 1] Japanese Kohyo (Examined) Publication S62-49247
[Patent Document 2] Japanese Kokai (Unexamined) Publication 2003-40736
[Patent Document 3] Japanese Kokai (Unexamined) Publication S60-69011